It's a button problem. Well, no really a "problem", just button finishing quality.
I had the same issue with volume rocker, it would make clicking sound when pressed, or get stuck on volume down.
I went to service, they asked me to wait few days for replacement. So I took it back home, pull it out, file it with wife's nail filer, put it back in and it works better than stock.
There was a tiny bit of extra plastic, barely noticeable, you had to touch it to feel the tiny bump. I suspect it's the same case with the home button.